[alsa-devel] [PATCH] ALSA: hda - Don't overwrite the pin default configs

[Takashi Iwai]

At Thu, 22 Nov 2012 18:02:34 +0100,
David Henningsson wrote:
> 
> On 11/22/2012 05:51 PM, Takashi Iwai wrote:
> > Since we keep the pin default config values anyway internally, we
> > don't have to set the values in the codec.  This patch removes the
> > code writing the pincfg values.
> >
> > As a gratis bonus, we can remove also the code restoring the original
> > pincfg values at PM resume or module free.  This will give us more
> > benefit, as it can reduce the unnecessary power-up of codecs.
> >
> > This won't change the driver functionality.  The only difference would
> > be that the codec proc file will show the original pincfg values
> > instead of the actually referred values.  The actually referred values
> > can be determined from sysfs *_pin_configs files.
> > (Also hda-emu was updated to follow this change.)
> >
> > Signed-off-by: Takashi Iwai <tiwai at suse.de>
> > ---
> >
> > David, this change may hit your QA test.  As mentioned, the only
> > difference is the default pincfg outputs in proc files.
> 
> Thanks. I don't think it'll hit my testing as hda-emu and 
> hda-jack-retask both read from the sysfs where available.
> 
> Not powering up the codecs might need some careful testing though? I 
> remember the ivybridge-hdmi error (which I sent a patch for recently) 
> was less likely to occur if codec was powered up after resume.

In the PM path, there is almost zero impact about the power usage.
It's anyway powered up at the resume.  Just a few verb sequences can
be reduced by this.

But for the module unload or the shutdown, this can be a benefit, as
this can avoid unnecessary power up just for shutting down.


Takashi